# Phase-frustrated vortical and skyrmionic lattices in coherently coupled three-component Bose–Einstein condensates

**Datum:**18 januari 2016

**Locatie:**Universiteit Antwerpen - Campus Groenenborger - Room U.241 - Groenenborgerlaan 171

**Tijdstip:**16 - 17 uur

**Organisatie / co-organisatie:**Condensed Matter Theory (CMT)

**Korte beschrijving:**(POSTPONED) Condensed Matter Theory seminar presented by Natalia Orlova

**Phase-frustrated vortical and skyrmionic lattices in coherently coupled three-component Bose–Einstein condensates**

## Condensed Matter Theory seminar given by:

**Natalia Orlova** from the CMT group @UAntwerp

**Title:** Phase-frustrated vortical and skyrmionic lattices in coherently coupled three-component Bose–Einstein condensates

**Abstract:** We studied numerically harmonically trapped and coherently-coupled three-component Bose-Einstein condensate(BEC). Such system is based on a three level atom where the population of BEC is oscillating between three hyperfine spin states resulting in the system being in the superposition of these states. Effective Rabi frequencies (couplings);couple hyperfine spin states through their phases due to which a phase difference arises between the components. The sign of the Rabi coupling can be manipulated via detuning. For a two-component Rabi-coupled BEC the sign of the Rabi coupling does not play an important role, because the Rabi energy will tend to be always attractive, and as a result at a strong Rabi coupling the phase difference between the components will vanish. But for a three-component coherently-coupled BEC the situation changes dramatically. If we choose one of couplings to be negative, then the phase differences between the components can never be zero simultaneously resulting in some of Rabi couplings will be strongly suppressed.

We showed that our system can host unconventional vortex lattices in its rotating ground state. The discovered lattices incorporate square patterns, vortex dimers and chains, and doubly quantized vortices. They arise due to the interplay of the repulsive density-density and attractive Rabi couplings as well as due to the Rabi coupling becoming suppressed. Some of the vortex lattice solutions were classified as skyrmions for which we showed that the average spin rotates in three-dimensional space. We also calculated the topological invariant for skyrmionic solutions.

Because of this Rabi suppression that stems from phase frustration, domain walls in the relative phases can persist between some components even at strong Rabi coupling, while vanishing between others.

**Contact e-mail:**lucian.covaci@uantwerpen.be

**Link:**https://www.uantwerpen.be/cmt